Lecture 4: Regulation of Blood Pressure

Cardiac output

Volume of blood pumped through the heart per unit time

Cardiac output (mL/min)= stroke volume (mL/beat) X Heart rate (bpm)

Ohm’s Law

Blood flow (F) directly proportional to difference in pressure (delta P)

Blood flow (F) indirectly proportional to resistance (R)

Pressure diff: V=I/R, voltage

Blood flow: I=V/R, current

Resistance: R=V/I, Resistance

Blood pressure monitoring

Body controls bp when cardiac output is increased to service tissues

Baroreceptors

Stretch- sensitive mechanoreceptor neurons, located mostly in the carotid and pulmonary arteries, aorta, and heat

Arterial Baroreceptor

Aortic arch, carotid arteries

Sensitive to short term change

More stretch= increased firing rate

Low pressure Baroreceptor

Large systemic veins, pulmonary vessels, RA and R/LV

Affect circulation and kidneys (fluid retention)

Baroreflex

Rapid negative feedback loop

1. Baroreceptor activated by blood volume of stretching of arterial wall

2. Activated BR send signals to brain

3. Signals from brain sent to vessels/heart to reduce bp

decreased P X decreased R= decreased in delta P

Hypertension

too high blood pressure

Core mechanism: mechanical stress on artery wall; increased heart workload

Chronic damage: harmful consequences of often occur slowly and silently

Heart

• Left ventricular hypertrophy

• Heart failure

• Coronary artery disease, heart attack

• Atrial fibrillation

Vessels

• Arterial thickening and stiffening

• Bulging/ballooning of vessels

• Rupture in vessel wall causing hemorrhage

• Peripheral artery disease

• Thrombosis

• Brain, kidneys, eyes, reproductive

Hypotension

Too low blood pressure

CM: inadequate perfusion

can frequently have rapid, acute effects

Shock

• acute and severe

• Tissues don’t get enough O2/nutrients, waste buildup

• Organs with highest metabolic demand suffer 1st

Brain, kidneys, heart, gut, lungs, blood